Sorption Study of a Starch Biopolymer as an Alternative Desiccant for Energy Wheels

The sorption of water vapor on high amylose starch was investigated as an alternative desiccant for air-to-air energy exchangers used in ventilation units. Sorption performance of micron-sized mesoporous high amylose starch (HAS15, dp = 15 μm, Pw = 46 Å) and two mesoporous silica gel samples (SG13, dp = 13 μm, Pw = 62 Å; Pw = 62 Å; SG55, dp = 55 μm, Pw = 77 Å) were studied and compared. Transient water vapor sorption tests were performed using small-scale energy exchangers coated with HAS15 and silica gel. Although N2 gas adsorption tests showed lower sorption capacity for HAS15 compared to the silica gel samples, higher sorption rates and uptake capacity were shown for HAS15 when measured by water vapor transient sorption results. In addition, the latent effectiveness, an indicator of moisture recovery efficiency for exchangers, was calculated for each exchanger. With the same amount of desiccant coated on the energy exchanger channels, the latent effectiveness of the HAS-coated material was 2%–13% greater than that of the silica gel materials, depending on the operating conditions.